The All Motor Build Report

When we last posted (The 2GN SOHC 2.0l Group 2 All Motor Build), the plan was a pile of parts on a shelf and some boxes had just started to arrive from Modern Performance. Our donor block had been cleaned up and the crank checked. A clean area was setup and covered using recycled boxes from our kitchen cabinets.

Just like standalone engine management, the key here is to take your time and methodically go through the build step by step. I have rebuilt a bottom end a couple of times, but this was the first time assembling the whole machine from scratch. All of the running gear for the camshaft was needed, along with all of the miscellaneous brackets and bolts, the intake manifold, etc. I found a wonderful 2005 donor in the junkyard on a “50% off” weekend.

When installing Piston Rings: Read the page that came with your pistons. Read it again! I looked at the chart about 20 times, it said: Bore x .0056″ and when I tested the rings, right away the gap was almost .015″. Incorrect rings? I ask around and after a few inquiries it is brought to my attention that Bore x .0056″ actually means ([bore size 3.445] multiplied by [0.0056] equals [0.0193]) I completely missed that it was a little math problem. I get through the steps of filing down the rings, wiping off the metal, hitting with oil, wiping again, and testing. After the first couple I get the hang of it and can guess when I’m close after dragging the gap over a file 5-6 times. The most important piece I picked up here is this: Blow-by is bad, but having the rings expand to the point where the ends crash into each other is worse. There was no “stage rally” listed on the JE Piston chart, so I went with “Circle Track / Drag Race” numbers over “Street Strip” knowing that the engine will be going flat out from 3100 to 6500 for a 15 miles at a time. 🙂

Why the factory intake Kris?! I had tuned into two posts in particular for that decision: The first was a comprehensive intake dyno test over on neons.org which showed that while the ITB’s and AMM intakes are great, they are great at making power OVER 7,000 RPM. I knew the 2.0L SOHC could make low end torque and the long intake is especially part of that. Second is a post where Vincent slapped a 2GN intake on a 1995 SOHC 1GN and proceeded to make 5HP and almost 10lbs of torque!

No long tube header?! Two things come into play here: I wanted the ability to keep the stock exhaust and the stock catalytic converter location, and just like the short intakes – the long headers make more power at higher RPM, sometimes at the detriment of low end torque.

The 3 day weekend was as good time to swap the new motor in. I finally decided to delete the AC, as it’s 5 complicated connections and like 20lbs of parts. I made a good effort to get it going, but all of those seals need to be clean-room clean, and any time I have to pull the motor in the future a fragile system of vacuum, refrigerant, and O-rings need to be “dealt with.”

Start’er up! The only change I had to make with the Megasquirt over the stock motor is the crank signal is different on the pre-2003 Neons. I made one change in a drop-down menu, clicked burn, power cycled, and started the car! Literally “crank, crank, vroom.” It startled me as I expected to have to fiddle with something for 15 minutes. Before I knew it, the new engine was up to temp. I ran it at various RPM’s for a few minutes after warm-up and triple checked everything.

A few days before my dyno appointment I got the knock sensor working. This required me to solder the spark signal from the MSX board OR re-run new wires to the engine bay. I chose to change it inside the Megasquirt. I did this and the next night got some weird readings that maybe my spark timing was off, so I went back to basics. I checked timing and it was off! 😮 At this very moment the mechanical tensioner that WAS making a little noise earlier, decided to full on rattle and ping itself – loudly. I thought for sure the belt had skipped a tooth. Time to pull it all apart and get to the timing belt. 🙁

Getting it all apart meant pulling the under-drive pulley and rocking the motor up and down like 25 degrees to get the motor mount / timing cover off. Once in there though, I discovered that the timing was fine. The tensioner was too TIGHT and pulling on the belt made the same rattle and ping so I adjusted it into the sweet spot. Put it all back together and sleep on it. More reading the next day revealed that when you change the timing to fixed and set it more than 10 degrees, you need to power cycle the MS. I re tested it – 0.0 on the MS and TDC on the car. No more noise from the timing belt tensioner at least.

To the Dyno!

Wide open throttle run on the DynaPack.

The tech at Church Auto Testing made quick work of the fuel map that I had been fiddling with for many days and weeks. He then turned his attention to the ignition timing (the critical reason WHY you need dyno testing) and the engine responded to timing changes without issue. He also set the limiter, fix the hot engine start-up, etc. A couple of runs later the new engine I built was making 143HP and 150ft/lbs of torque! By comparison, a bone stock SOHC 2.0l makes about 112HP and 115ft/lbs at the wheels, and it’s equal to a stock 2.4l Stratus motor (a common engine swap for the Neon). All this with the stock cat back, no timing change on the adjustable cam gear, and a table switch on the dash prepared for a tank of 100+ octane fuel. I’ve got a strong motor, a good baseline, and room to grow! 😀